Antibiotic AT-125 (U-42,126), producible by culturing Streptomyces sviceus in an aqueous nutrient medium has the following structure: ##EQU2##
The absolute configuration of AT-125 was determined to be (.alpha.S, 5S)-.alpha.-amino-3-chloro-2-isoxazoline-5-acetic acid. Like U-43,795, it is also an amphoteric compound and can exist in different ionic forms according to the pH of the environment. At low pH, AT-125 exists in the acid-addition salt form, at a higher pH, in a zwitterion form, and at still higher pH in a metal salt form.
Also, AT-125 inhibits the growth of Bacillus subtilis, Saccharomyces pastorianus, Penicillium oxalicum, Candida albicans, Saccharomyces cerevisiae and Escherichia coli, and can be used to inhibit such microorganisms in various environments.